According to conventional high frequency signal interpolation, an interpolation signal is generated through frequency conversion of a signal to be interpolated, as disclosed in Japanese Unexamined Patent Application Publication No. 2004-184472 (hereafter referred to as Patent Document 1). Moreover, as disclosed in Japanese Unexamined Patent Application Publication No. Hei 1-131400 (hereafter referred to as Patent Document 2), a high frequency signal without correlation with an original signal is added. That is, the conventional high frequency signal interpolation is carried out through frequency conversion and thereby generating an interpolation signal, or adding a high frequency signal without correlation with an original signal.